The long-term goal of this proposal is to develop recombinant cell-penetrating antibodies or transbodies for the treatment or prevention of neurological disease. Antibodies that function intracellularly (intrabodies) show great potential as neuroprotective reagents for reducing the toxic accumulation of misfolded proteins underlying several human neurodegenerative disorders, including Huntington's, Parkinson's, Alzheimer's, and prion diseases. However, the practical application of intrabodies is currently hampered by a lack of robust gene or protein delivery systems for administering these recombinant therapeutic proteins effectively in vivo. This application hypothesizes that the novel ability of certain autoantibodies to penetrate cells can be harnessed to target recombinant therapeutic proteins such as intrabodies into neurons for therapeutic applications. Preliminary data using a lead therapeutic intrabody fused to a benign anti-DNA transbody that penetrates neurons through ENT2/SLC29A2 equilibrative nucleoside transporters offer proof of concept for this experimental approach. Using models of Huntington's disease as a disease paradigm for protein aggregation disorders, the specific aims of this proposal are three-fold: (i) to optimize recombinant transbody domains from naturally-occurring antibodies that penetrate cells, (ii) test a lead anti-huntingtin intrabody in fusion with optimized transbodies for cell penetration and functional efficacy in a cellular model of Huntington's disease, and (iii) evaluate anti-huntington transbodies for therapeutic potential in vivo using a transgenic mouse model of Huntington's disease. The experiments outlined in this proposal ultimately address what is currently a critical barrier for gene or protein therapies, namely achieving widespread and efficient delivery of recombinant therapeutic protein into neurons, for a subset of neurological conditions where intracellular correction is desired. PUBLIC HEALTH RELEVANCE: This application develops and tests cell-permeable antibodies or transbodies as specific agents for treating and preventing human neurological disease, using models of Huntington's disease, a lethal neurodegenerative disorder estimated to affect 1 in 10,000 Americans, as a disease paradigm. The methodologies tested in this proposal, if successful, may be directly applicable to other kinds of molecular therapies for which transport into diseased neurons is currently inefficient or unattainable.